Metal–organic frameworks (MOFs) have been extensively used for single‐site catalysis and light harvesting, but their application in multicomponent photocatalysis is unexplored. We report here the ...successful incorporation of an IrIII photoredox catalyst and a NiII cross‐coupling catalyst into a stable Zr12 MOF, Zr12‐Ir‐Ni, to efficiently catalyze C−S bond formation between various aryl iodides and thiols. The proximity of the IrIII and NiII catalytic components to each other (ca. 0.6 nm) in Zr12‐Ir‐Ni greatly facilitates electron and thiol radical transfers from Ir to Ni centers to reach a turnover number of 38 500, an order of magnitude higher than that of its homogeneous counterpart. This work highlights the opportunity in merging photoredox and organometallic catalysts in MOFs to effect challenging organic transformations.
Business merger: The incorporation of both an IrIII photoredox catalyst and a NiII cross‐coupling catalyst into a stable Zr12 metal–organic framework (MOF) affords a solid dual photocatalyst for C−S coupling between aryl iodides and thiols. By facilitating electron and thiophenol radical transfers from Ir to Ni centers, the MOF photocatalyst exhibits an order of magnitude higher catalytic activity than its homogeneous counterpart.
Na‐ion capacitors have attracted extensive interest due to the combination of the merits of high energy density of batteries and high power density as well as long cycle life of capacitors. Here, a ...novel Na‐ion capacitor, utilizing TiO2@CNT@C nanorods as an intercalation‐type anode and biomass‐derived carbon with high surface area as an ion adsorption cathode in an organic electrolyte, is reported. The advanced architecture of TiO2@CNT@C nanorods, prepared by electrospinning method, demonstrates excellent cyclic stability and outstanding rate capability in half cells. The contribution of extrinsic pseudocapacitance affects the rate capability to a large extent, which is identified by kinetics analysis. A key finding is that ion/electron transfer dynamics of TiO2@CNT@C could be effectively enhanced due to the addition of multiwalled carbon nanotubes. Also, the biomass‐derived carbon with high surface area displays high specific capacity and excellent rate capability. Owing to the merits of structures and excellent performances of both anode and cathode materials, the assembled Na‐ion capacitors provide an exceptionally high energy density (81.2 W h kg−1) and high power density (12 400 W kg−1) within 1.0–4.0 V. Meanwhile, the Na‐ion capacitors achieve 85.3% capacity retention after 5000 cycles tested at 1 A g−1.
High‐performance Na‐ion capacitors are fabricated with TiO2@CNT@C nanorods as an intercalation‐type anode and biomass‐derived carbon as an ion adsorption cathode in an organic electrolyte. Owing to the state‐of‐the‐art architectures, excellent electrochemical performances, and perfect match in both electrodes, the hybrid devices demonstrate high energy‐power integration and good cyclic stability.
Metal–organic layers (MOLs), a free-standing monolayer version of two-dimensional metal–organic frameworks (MOFs), have emerged as a new class of 2D materials for many potential applications. Here we ...report the design of a new photosensitizing MOL, Hf12-Ru, based on Hf12 secondary building units (SBUs) and Ru(bpy)32+ (bpy = 2,2′-bipyridine) derived dicarboxylate ligands. After modifying the SBU surface of Hf12-Ru with M(bpy)(CO)3X (M = Re and X = Cl or M = Mn and X = Br) derived capping molecules through carboxylate exchange reactions, the resultant Hf12-Ru-Re and Hf12-Ru-Mn MOLs possess both Ru(bpy)32+ photosensitizers and M(bpy)(CO)3X catalysts for efficient photocatalytic CO2 reduction. The proximity of the MOL skeleton to the capping ligands (1–2 nm) facilitates electron transfer from the reduced photosensitizer Ru(bpy)3+ to MI(bpy)(CO)3X (M = Re, Mn) catalytic centers, resulting in CO2 reduction turnover numbers of 8613 under artificial visible light and of 670 under sunlight. MOLs thus represent a novel platform to assemble multifunctional materials for studying artificial photosynthesis.
Abstract
Porous organic polymers (POPs) have emerged as a novel class of porous materials that are synthesized by the polymerization of various organic monomers with different geometries and ...topologies. The molecular tunability of organic building blocks allows the incorporation of functional units for photocatalytic organic transformations. Here, we report the synthesis of two POP‐based photocatalysts via homopolymerization of vinyl‐functionalized diaryl dihydrophenazine (DADHP) monomer (
POP1
) and copolymerization of vinyl‐functionalized DADHP and 2,2′‐bipyridine monomers (
POP2
). The fluorescence lifetimes of DADHP units in the POPs significantly increased, resulting in enhanced photocatalytic performances over homogeneous controls.
POP1
is highly effective in catalysing visible‐light‐driven C−N bond forming cross‐coupling reactions. Upon coordination with Ni
2+
ions,
POP2‐Ni
shows strong synergy between photocatalytic and Ni catalytic cycles due to the confinement effect within the POP framework, leading to high efficiency in energy, electron, and organic radical transfer.
POP2‐Ni
displays excellent activity in catalysing C−P bond forming reactions between diarylphosphine oxides and aryl iodides. They increased the photocatalytic activities by more than 30‐fold in C−N and C−P cross‐coupling reactions. These POP catalysts were readily recovered via centrifugal separation and reused in six catalytic cycles without loss of activities. Thus, photosensitizer‐based POPs provide a promising platform for heterogeneous photocatalytic organic transformations.
More and more tourists are sharing their travel feelings and posting their real experiences on the Internet, generating tourism big data. Online travel reviews can fully reflect tourists' emotions, ...and mining and analyzing them can provide insight into the value of them. In order to analyze the potential value of online travel reviews by using big data technology and machine learning technology, this paper proposes an improved support vector machine (SVM) algorithm based on travel consumer sentiment analysis and builds an Hadoop Distributed File System (HDFS) system based on Map-Reduce model. Firstly, Internet travel reviews are pre-processed for sentiment analysis of the review text. Secondly, an improved SVM algorithm is proposed based on the main features of linear classification and kernel functions, so as to improve the accuracy of sentiment word classification. Then, HDFS data nodes are deployed on the basis of Hadoop platform with the actual tourism application context. And based on the Map-Reduce programming model, the map function and reduce function are designed and implemented, which greatly improves the possibility of parallel processing and reduces the time consumption at the same time. Finally, an improved SVM algorithm is implemented under the built Hadoop platform. The test results show that online travel reviews can be an important data source for travel big data recommendation, and the proposed method can quickly and accurately achieve travel sentiment classification.
The magnetic properties of many magnetic materials can be controlled by external stimuli. The principal focus here is on the thermal, photochemical, electrochemical, and chemical control of phase ...transitions that involve changes in magnetization. The molecular compounds described herein range from metal complexes, through pure organic compounds to composite materials. Most of the Review is devoted to the properties of valence‐tautomeric compounds, molecular magnets, and spin‐crossover complexes, which could find future application in memory devices or optical switches.
Under control: The behavior of certain magnetic materials can be controlled by external stimuli such as temperature, light, and pressure. Typical examples of such switchable materials are valence‐tautomeric compounds, molecular photomagnets, and spin‐crossover complexes, which could find application in memory devices or optical switches.
The jet breaks in the afterglow light curves of short gamma-ray bursts (SGRBs), rarely detected so far, are crucial for estimating the half-opening angles of the ejecta (θj) and hence the neutron ...star merger rate. In this work, we report the detection of jet decline behaviors in GRB 150424A and GRB 160821B, and find θj ∼ 0.1 rad. Together with five events reported before 2015 and three others "identified" recently (GRB 050709, GRB 060614, and GRB 140903A), we have a sample consisting of nine SGRBs and one long-short GRB with reasonably estimated θj. In particular, three Swift bursts in the sample have redshifts z ≤ 0.2, with which we estimate the local neutron star merger rate density to be or if the narrowly beamed GRB 061201 is excluded. Inspired by the typical θj ∼ 0.1 rad found currently, we further investigate whether the off-beam GRBs (in the uniform jet model) or the off-axis events (in the structured jet model) can significantly enhance the GRB/GW association. For the former, the enhancement is at most moderate, while for the latter the enhancement can be much greater and a high GRB/GW association probability of ∼10% is possible. We also show that the data of GRB 160821B may contain a macronova/kilonova emission component with a temperature of ∼3100 K at ∼3.6 days after the burst and more data are needed to ultimately clarify.
Very recently the NICER collaboration published the first-ever accurate measurement of mass and radius together for PSR J0030+0451, a nearby isolated quickly rotating neutron star (NS). In this work ...we set the joint constraints on the equation of state (EoS) and some bulk properties of NSs with the data of PSR J0030+0451, GW170817, and some nuclear experiments. The piecewise polytropic expansion method and the spectral decomposition method have been adopted to parameterize the EoS. The resulting constraints are consistent with each other. Assuming the maximal gravitational mass of nonrotating NS MTOV lies between 2.04M and 2.4M , with the piecewise method the pressure at twice nuclear saturation density is measured to be at the 90% level. For an NS with canonical mass of 1.4M , we have the moment of inertia , tidal deformability , radius , and binding energy at the 90% level, which are improved in comparison to the constraints with the sole data of GW170817. These conclusions are drawn for the mass/radius measurements of PSR J0030+0451 by Riley et al. For the measurements of Miller et al., the results are rather similar.
Salt stress can significantly affect plant growth and agricultural productivity. Receptor-like kinases (RLKs) are believed to play essential roles in plant growth, development, and responses to ...abiotic stresses. Here, we identify a receptor-like cytoplasmic kinase, salt tolerance receptor-like cytoplasmic kinase 1 (STRK1), from rice (Oryza sativa) that positively regulates salt and oxidative stress tolerance. Our results show that STRK1 anchors and interacts with CatC at the plasma membrane via palmitoylation. CatC is phosphorylated mainly at Tyr-210 and is activated by STRK1. The phosphorylation mimic form CatCY210D exhibits higher catalase activity both in vitro and in planta, and salt stress enhances STRK1-mediated tyrosine phosphorylation on CatC. Compared with wild-type plants, STRK1-overexpressing plants exhibited higher catalase activity and lower accumulation of H2O2 as well as higher tolerance to salt and oxidative stress. Our findings demonstrate that STRK1 improves salt and oxidative tolerance by phosphorylating and activating CatC and thereby regulating H2O2 homeostasis. Moreover, overexpression of STRK1 in rice not only improved growth at the seedling stage but also markedly limited the grain yield loss under salt stress conditions. Together, these results offer an opportunity to improve rice grain yield under salt stress.
Recent interest has surged in using heterogeneous carriers to boost synergistic photocatalysis for organic transformations. Heterogeneous catalysts not only facilitate synergistic enhancement of ...distinct catalytic centers compared to their homogeneous counterparts, but also allow for the easy recovery and reuse of catalysts. This mini‐review summarizes recent advancements in developing heterogeneous carriers, including metal–organic frameworks, covalent–organic frameworks, porous organic polymers, and others, for synergistic catalytic reactions. The advantages of porous materials in heterogeneous catalysis originate from their ability to provide a high surface area, facilitate enhanced mass transport, offer a tunable chemical structure, ensure the stability of active species, and enable easy recovery and reuse of catalysts. Both photosensitizers and catalysts can be intricately incorporated into suitable porous carriers to create heterogeneous dual photocatalysts for organic transformations. Notably, experimental evidence from reported cases has shown that the catalytic efficacy of heterogeneous catalysts often surpasses that of their homogeneous analogues. This enhanced performance is attributed to the proximity and confinement effects provided by the porous nature of the carriers. It is expected that porous carriers will provide a versatile platform for integrating diverse catalysts, thus exhibiting superior performance across a range of organic transformations and appealing prospect for industrial applications.
Porous materials including metal–organic frameworks (MOFs), covalent–organic frameworks (COFs), and porous organic polymers (POPs) have recently been established as an ideal platform to enhance synergistic photocatalysis for organic transformations. Benefitting from the designability of these molecular materials, both photosensitizers and catalysts can be intricately incorporated into the porous carriers, leading to greatly enhanced performance over their homogeneous counterparts.
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